Time for an 2014 update…

Task/Fibonacci-sequence/Perl/fibonacci-sequence-1.pl

@@ -1,9 +1,32 @@
-sub fibIter {
-    my $n = shift;
-    return $n if $n < 2;
+# Iterative Fibonacci with bignum support.
+# Multi-licensed under your choice of:
+# 1. The GNU Free Documentation License (GFDL).
+# 2. The MIT/X11 license.
+# 3. The GNU General Publice License (GPL).
+# 4. The Public Domain as understood by the CC-Zero public domain dedication.
 
-    my $fibPrev = 1;
-    my $fib = 1;
-    ($fibPrev, $fib) = ($fib, $fib + $fibPrev) for 2..$n-1;
-    $fib;
+use strict;
+use warnings;
+
+use Math::BigInt try => 'GMP';
+
+sub fib_iter
+{
+    my ($n) = @_;
+
+    my $this_fib = Math::BigInt->new(0);
+    my $next_fib = Math::BigInt->new(1);
+
+    my $pos = 0;
+
+    while ($pos < $n)
+    {
+        ($this_fib, $next_fib) = ($next_fib, $this_fib+$next_fib);
+    }
+    continue
+    {
+        $pos++;
+    }
+
+    return $this_fib;
 }